The present invention relates to a spring-loaded brake cylinder which is used, in particular, in commercial vehicles.
A spring-loaded brake cylinder of this type usually has a housing, in which a spring-loaded brake piston is guided. The piston divides the interior of the housing into a spring-loaded brake chamber which can be loaded with pressure and a spring chamber which receives an accumulator spring. The accumulator spring is arranged in the spring chamber in such a way that it prestresses the spring-loaded brake piston in the direction of the spring-loaded brake chamber. In order that a vehicle which has been parked or braked and in which the spring-loaded brake cylinder is arranged can be moved, the spring-loaded brake chamber is loaded with compressed air in such that the spring-loaded brake piston is displaced counter to the spring force of the accumulator spring. As a result, a brake device which is coupled to the spring-loaded brake piston moves out of engagement with a brake disk or the like, with the result that the vehicle is no longer being braked. For brake actuations while driving, a spring-loaded brake cylinder of this type can be coupled to a service brake cylinder in a known way.
If a substantial reduction in the air pressure in the spring-loaded brake chamber occurs on account of a pressure drop in the system, then the spring-loaded brake piston is displaced in the direction of the spring-loaded brake chamber, on account of the prestress of the accumulator spring, in such a way that the brake device, which is coupled to the spring-loaded brake piston, grips and carries out braking of the vehicle. In this way, a commercial vehicle is reliably prevented from continuing to drive in an unbraked manner and therefore being difficult to control, for example in the case of a line rupture of the brake pressure line during driving. This emergency braking in the case of a lack of compressed air feed is additionally also used in trailers, etc., which are parked for a relatively long time, in order that said vehicles can be prevented from rolling away unintentionally.
However, it is to be possible for the braking action, which is exerted in such cases by the mechanical accumulator spring in the spring-loaded brake cylinder, to be released again, for example in order to move parked vehicles or in order to clear a driving lane which is blocked on account of a breakdown, in order that the relevant vehicles can be moved and, for example, traffic obstructions can be eliminated.
Since, however, the available compressed air supply is frequently damaged here by lines being torn off, etc. and cannot be used and there is also no replacement compressed air supply, it is necessary in practice that spring-loaded brake cylinders of this type have a mechanical emergency release device. This is usually provided with an actuating device in the form of a threaded spindle which is accessible from outside and can be actuated in a rotatable manner.
Here, the threaded spindle interacts in a known construction, as described in DE 198 30 154 A1, with an output element which is arranged in a stationary manner in the axial direction on the housing of the spring-loaded brake cylinder, such as a nut, with the result that a rotation of the threaded spindle brings about a linear displacement of the same. In this concrete embodiment, the inner end of the threaded spindle in the axial direction is configured, for example, with a projection which can be brought into contact with a bearing face on the spring-loaded piston. On account of the linear movement of the threaded spindle in the axial direction, which is initiated by the rotational movement, a likewise linear displacement of the spring-loaded piston occurs counter to the prestressing force of the accumulator spring, so that, as a result, the brake device which interacts with the spring-loaded piston can be released.
This construction has proven itself in practice with regard to its functionality. However, it has the disadvantage that the threaded spindle has to be screwed relatively far out of the housing for mechanical emergency release, which leads to a considerable space requirement on the side of the spring-loaded brake cylinder. However, such a space is provided in the commercial vehicle for other components or is restricted by other moving components.
In order to counteract this problem, WO 02/44004 proposes a different construction of the mechanical emergency release device. In this proposed design, the threaded spindle is fixed in a stationary manner in the axial direction on the housing of the spring-loaded brake cylinder. At the same time, however, the threaded spindle is mounted rotatably and is provided at the end which is accessible from outside with an action face for a turning tool, such as with a hexagonal head or the like, by means of which the threaded spindle can be set in rotation. This threaded spindle engages into a central cavity of the spring-loaded piston, the threaded spindle being in engagement here with a hexagonal nut which is mounted in the interior of the spring-loaded piston such that it cannot be rotated, but can be displaced in the axial direction. In order to release the spring-loaded brake, the threaded spindle is actuated rotationally here such that the nut, which runs on it, is guided against a bearing face on the spring-loaded piston and, if the threaded spindle is turned further, drives the spring-loaded piston counter to the prestress of the accumulator spring. This construction has the substantial advantage that no clearance is required on the exterior of the cylinder for a threaded spindle which needs to be screwed out.
Furthermore, the known emergency release device has an indicator device with an indicator rod which points to a display section. Here, the indicator rod extends through the threaded spindle centrally and is guided in it such that a movement is possible in the axial direction. Here, the indicator rod is prestressed against a stepped section in the threaded spindle by a spring such that the display section is pressed to the outside. Depending on whether the spring-loaded brake cylinder is situated in the emergency released state or not, the display section of the indicator rod protrudes beyond the threaded spindle to the outside or is recessed in it, which represents a visible signal for the state of the spring-loaded brake cylinder.
Arranged at that end of the indicator rod, which is remote from the display section, is a disk. The disk is arranged transversely with respect to the axial direction, serves as a stop, and protrudes on the circumferential side in such a way that the outer edge of the disk can come into contact with the nut. Here, the disk is fixed by a locking washer on the control section of the indicator rod. Since, however, components of the emergency release device such as this disk and its locking washer are arranged in the interior of the spring-loaded brake cylinder, their assembly is made more difficult, however.
It is therefore an object of the present invention to develop a spring-loaded brake cylinder such that it can be assembled more simply and less expensively.
This object is achieved by a spring-loaded brake cylinder for vehicles, having at least one spring-loaded brake piston which can be actuated by an accumulator spring. The piston is mounted in a housing, and is delimited on one side by a spring-loaded brake chamber and on the opposite side by a spring chamber which receives the accumulator spring and is connected to a spring-loaded piston rod. A mechanical emergency release device is provided for the emergency release of the spring-loaded brake cylinder. An axial displacement of the spring-loaded brake piston counter to the prestress of the accumulator spring is brought about by way of the emergency release device. The emergency release device has a threaded spindle which is fixed rotatably on the housing and is in engagement with an axially displaceable transmission device which is held non-rotatably in the emergency release device. The transmission device is brought into contact with a bearing face on the spring-loaded brake piston for the emergency release of the spring-loaded brake cylinder. An indicator device includes an indicator rod which indicates the position of the spring-loaded brake piston. The rod reaches through the threaded spindle and can be displaced in the axial direction with respect to the latter. A stop body which can be brought into engagement with the transmission device is arranged in the region of one end of the indicator rod. The stop body is connected positively to the indicator rod by a latching connection which is produced by an axial relative movement between the indicator rod and the stop body.
The invention provides for the stop body to be connected positively by a latching connection, which is produced by way of an axial relative movement between the indicator rod and the stop body. The connection between the indicator rod and the stop body can then be produced merely by means of the relative movement, without it being necessary for this purpose, however, that access to the connecting point is possible. Rather, the relative movement can be caused from the exterior, that is to say from outside the housing, for example by the fact that the indicator rod is inserted from the outside into the through opening of the threaded spindle which is provided for it, to such a depth that its end latches with the stop body. In comparison with the prior art according to WO 02/44004 discussed above, this results in the advantage that a locking washer no longer has to be mounted to hold the disk, which serves there as a stop body, and the production outlay is reduced in comparison.
Particularly preferably, at least in the region of one edge of a receiving opening for the end of the indicator rod, the stop body is of an elastic configuration such that the edge of the receiving opening can be passed and reached behind by an annular collar which is formed on the end of the indicator rod and has a greater diameter than the diameter of the receiving opening, on account of the relative movement between the indicator rod and the stop body.
In particular, the stop body can be supported on the spring-loaded brake piston rod in a sprung manner by way of spring means if the indicator rod is moved axially with respect to the stop body in order to produce the latching connection.
A particularly space-saving arrangement results if the stop body has a cup-shaped configuration, with a bottom which has the receiving opening and with a casing wall which is guided linearly in the spring-loaded brake piston rod, and if the opening of the cup-shaped stop body points away from the indicator rod and the spring means are enclosed at least partially by its casing wall. Moreover, tilt-free mounting of the stop body in the spring-loaded brake piston rod is possible as a result of the flat casing wall. A lightweight construction results if the cup-shaped stop body is manufactured from at least one plastic material. The indicator rod can also be composed of plastic for the same reason.
According to one development of the above-mentioned measure, a central region of the cup-shaped stop body, which central region has the receiving opening, can be configured as a central component which has a greater elasticity than the remaining stop body. The stop body is then guided by its casing wall which is more rigid in comparison, while the latching with the indicator rod is facilitated by the central component which is more elastic in comparison.
In the prior art according to WO 02/44004, the head of the threaded spindle which protrudes out of the housing is configured in multiple pieces, a projection face for applying a tool to the threaded spindle in order to set it in rotation being formed by a separate sleeve. According to one particularly preferable embodiment, the tool projection for applying the tool is manufactured on the threaded spindle in one piece with the latter, which results in an advantageous reduction in the number of parts of the emergency release device.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one preferred embodiment when considered in conjunction with the accompanying drawings.